The invention relates generally to turbo machines. More particularly, the invention relates to a steampath flow separation reduction system for a steam turbine.
The steampath efficiency in a steam turbine is a result of a multiple loss parameters and their interaction, these parameters are associated with aerodynamic and flow of fluids losses. Efforts have been made to understand and reduce those losses by improving blade profiles, reducing wall losses, gap losses and minimizing radial and circumferential efficiency variations as well as preventing flow separation.
Typically, it is desired to decrease the overall footprint of a steam turbine, for example, to develop less expensive steam turbines and to minimize the amount of necessary floor space to house the steam turbine. However, as the footprint of the steam turbine is decreased, the stages within the steam turbine are moved together, and the wall angles between the stages gets steeper. As wall angles increase, the steam flowing through the turbine, especially in low pressure sections, where wall angles are the highest, becomes agitated due to gaps and vortices, and flow separation occurs. Flow separation can cause significant steampath efficiency losses. Therefore, current systems tend to limit wall angles, especially in the low-pressure sections, to 45-50 degrees to prevent flow separation. Various attempts have been made to resdesign the steampath in order to reduce flow separation, including blade profile improvements and nozzle root modifications, such as using an L0 hump.